Allow photos to be displayed in ROWS instead of COLUMNS
When photos are displayed in columns it destroys any clear order to the photos. I put a good deal of thought into the ordering of the final set of images that I deliver at a wedding in order to tell the story in the strongest way possible. This is ruined with the "pinterest-style" display that shows photos in columns. Additionally it gives prominence to vertical images, whereas I find that most of my photos in general, and especially most of my favorite images, are horizontal.
Other similar proofing services have added the option to display in rows (shootproof, pixieset) and Instaproofs needs to do this as well.